Active matrix type display device

This invention is an active matrix type<u style="single">Color LCD</u>Regarding display devices.

FIG. 8 shows a transmission plan view of a part of the active substrate in an example of a conventional color liquid crystal display device, FIG. 9 shows a cross-sectional view taken along line XX of FIG. 8, and FIG. 10 shows a portion along line YY of FIG. It shows the cross-sectional view including the facing substrate in.

As shown in FIG. 10, in this color liquid crystal display device, the active substrate 1 and the opposing substrate 2 located above the active substrate 1 are bonded to each other via a substantially square frame-shaped sealing material (not shown). The liquid crystal 3 is enclosed in the space formed between the sealing material and both substrates 1 and 2.

Then, as shown in FIG. 8, a plurality of scanning lines 4 and a plurality of signal lines 5 are provided on the active substrate 1 extending in the row direction and the column direction, respectively. A thin film transistor 6 connected to both lines 4 and 5 and a pixel electrode 7 driven by the thin film transistor 6 are arranged in a matrix near each intersection of both lines 4 and 5. Further, the auxiliary capacitance line 8 is provided on the side opposite to the scanning line 4 by sandwiching the pixel electrode 7 so as to be overlapped with the pixel electrode 7 and extend in the row direction.

Next, a specific structure of the thin film transistor 6 and the like will be described with reference to FIG. A scanning line 4 including a gate electrode 11 is provided at a predetermined position on the upper surface of the active substrate 1 (opposing surface to the facing substrate 2), and an auxiliary capacitance line 8 is provided at another predetermined location, and the entire upper surface thereof is provided. Is provided with a gate insulating film 12.

A semiconductor thin film 13 made of intrinsic amorphous silicon is provided at a predetermined position on the upper surface of the gate insulating film 12. A channel protection film 14 is provided at substantially the center of the upper surface of the semiconductor thin film 13. Contact layers 15 and 16 made of n-type amorphous silicon are provided on both sides of the upper surface of the channel protection film 14 and on the upper surfaces of the semiconductor thin film 13 on both sides thereof.

A source electrode 17 is provided on the upper surface of one of the contact layers 15. A signal line 5 including a drain electrode 18 is provided at predetermined positions on the upper surface of the other contact layer 16 and the upper surface of the gate insulating film 12.

The thin film transistor 6 is composed of a gate electrode 11, a gate insulating film 12, a semiconductor thin film 13, a channel protective film 14, contact layers 15 and 16, a source electrode 17, and a drain electrode 18.

A flattening film 19 is provided on the entire upper surface of the gate insulating film 12 including the thin film transistor 6. A contact hole 20 is provided at a portion of the flattening film 19 corresponding to a predetermined portion of the source electrode 17. A pixel electrode 7 made of ITO is provided at a predetermined position on the upper surface of the flattening film 19. The pixel electrode 7 is connected to the source electrode 17 via the contact hole 20.

Next, the opposed substrate 2 will be described with reference to FIG. Black matrix 21 and color filter elements 22R, 22G, and 22B of R (red), G (green), and B (blue) are provided at each predetermined position on the lower surface of the facing substrate 2 (the surface facing the active substrate 1). Has been done. Of these, the color filter elements 22R, 22G, and 22B are provided so as to face the corresponding pixel electrodes 7.

A common electrode 23 made of ITO is provided on the lower surfaces of the black matrix 21 and the color filter elements 22R, 22G, and 22B. A pixel capacitance portion is formed by the pixel electrode 7, the common electrode 23 arranged opposite to the pixel electrode 7, and the liquid crystal 3 in between. In this case, since the area of the pixel electrode 7 is the same, the pixel capacitance of the pixel capacitance portion is the same.

Here, as shown in FIG. 8, the portion of the auxiliary capacitance line 8 that is overlapped with the pixel electrode 7 is the auxiliary capacitance electrode 8a. Then, the auxiliary capacitance portion is formed by the overlapped portion. In this case, since the area of the auxiliary capacitance electrode 8a is the same, the auxiliary capacitance of the auxiliary capacitance portion is the same.

By the way, the thicknesses of the color filter elements 22R, 22G, and 22B are different from each other for the purpose of correcting the transmitted light intensity of the liquid crystal 3 for each wavelength of R, G, and B. That is, the thickness of each of the color filter elements 22R, 22G, and 22B increases in this order.

On the other hand, since the pixel electrodes 7 corresponding to the color filter elements 22R, 22G, and 22B are provided on the flattening film 19, they are arranged on the same plane. Therefore, the gaps d1, d2, and d3 of each pixel of R, G, and B become smaller in this order. Such a structure is generally called a multi-gap structure.

Next, FIG. 11 shows an equivalent circuit of the conventional color liquid crystal display device. Reference numeral 31 indicates a pixel capacitance portion, 32 indicates an auxiliary capacitance portion, and 33 indicates a parasitic capacitance portion between the gate electrode 11 and the source electrode 17 of the thin film transistor 6. In this case, the common electrode 23, which is the electrode on the side of the pixel capacitance section 31 that is not connected to the thin film transistor 6, and the auxiliary capacitance electrode 8a, which is the electrode on the side that is not connected to the thin film transistor 6 of the auxiliary capacitance section 32, are a common power supply (voltage Vcom). It is connected to 34.

Next, FIG. 12 (a) shows the waveform of the signal voltage applied to the liquid crystal 3, and FIG. 12 (b) shows the scanning voltage (gate pulse) applied to the scanning line 4. Then, when the pixel capacitance of the pixel capacitance section 31 is Clc, the auxiliary capacitance of the auxiliary capacitance section 32 is Cs, and the parasitic capacitance of the parasitic capacitance section 33 is Cgs, the gate pulse is turned off and the image signal of each pixel is captured. At the end, the level shift voltage ΔV obtained by the following equation is generated at each pixel electrode potential Vsig. ΔV = (Cgs) / (Cgs + Clc + Cs)

This level shift voltage ΔV always lowers the pixel electrode potential Vsig by ΔV regardless of the polarity of the signal voltage applied to the signal line 5. Therefore, if the potential Vcom of the common electrode 23 is set lower than the central potential Vc of the signal line 5 by this level shift voltage ΔV, the voltage applied to the liquid crystal 3 becomes a waveform that is almost symmetrical in positive and negative directions, and flicker is prevented. be able to.

By the way, as described above, since the thicknesses of the color filter elements 22R, 22G, and 22B are thickened in this order, the gaps d1, d2, and d3 of the pixels of R, G, and B are reduced in this order. There is. The pixel capacitance Clc is represented by ε · S / d (ε: liquid crystal permittivity, S: pixel electrode area, d: gap).

Therefore, the pixel capacitance Clc increases as the gap d decreases. That is, in the case of R pixels, the gap d1 is the largest and the pixel capacitance Clc is the smallest, so that the level shift voltage ΔV is the largest. On the other hand, in the case of B pixel, the gap d3 is the smallest and the pixel capacitance Clc is the largest, so that the level shift voltage ΔV is the smallest.

<p> As described above, in the above-mentioned conventional color liquid crystal display device, there is a problem that the level shift voltage ΔV of each pixel of R, G, and B becomes smaller in this order, which causes flicker. An object of the present invention is to make the level shift voltage ΔV of each pixel of R, G, and B substantially the same.</p>

<p> The invention according to claim 1 is an active matrix type color liquid crystal display device in which the thickness of a color filter is different for each color component and any one of the color components is associated with each pixel. The color is the parasitic capacitance generated between the scanning line connected to the pixel electrode via the switching element and the pixel electrode so that the level shift voltage ΔV at the end of image signal acquisition is equal between the pixels. The pixels corresponding to the color components having a thick color filter are different from the pixels corresponding to the color components having a thin color filter, and the pixels are different from the pixels corresponding to the color components having a thin color filter. It is characterized in that the parasitic capacity generated on the contrary is large. The invention according to claim 2 is the invention according to claim 1, wherein the pixel electrode is formed on the upper layer side of the scanning line and overlaps with a part of the scanning line in the in-plane direction. Each of the pixels is formed, and the area of the polymerized portion is different according to the color component. According to the invention of claim 3, in the invention of claim 2, the pixels corresponding to the color component having a thick color filter are more than the pixels corresponding to the color component having a thin color filter. It is characterized in that the area of the polymerized portion is large. The invention according to claim 4 is an active matrix type color liquid crystal display device in which the thickness of the liquid crystal layer in each pixel is different for each color component, and the level shift voltage at the end of image signal acquisition between each pixel. The parasitic capacitance generated between the scanning line connected to the pixel electrode via the switching element and the pixel electrode is different for each pixel corresponding to the color component so that ΔV becomes equal, and the liquid crystal layer. A pixel having a thin thickness is characterized in that the parasitic capacitance generated for the pixel is larger than that of a pixel having a thick liquid crystal layer. The invention according to claim 5 is the invention according to claim 4, wherein the pixel electrode is formed on the upper layer side of the scanning line and overlaps with a part of the scanning line in the in-plane direction. Each of the pixels is formed, and the area of the polymerized portion is different according to the color component. The invention according to claim 6 is the invention according to claim 5, wherein the pixel having a thin liquid crystal layer has a larger area of the polymerized portion than the pixel having a thick liquid crystal layer. It is characterized by being present. The invention according to claim 7 is an active matrix type color liquid crystal display device in which the pixel capacitance is different for each color component, so that the level shift voltage ΔV at the end of image signal acquisition is equal between the pixels. , The parasitic capacitance generated between the scanning line connected to the pixel electrode via the switching element and the pixel electrode is different for each pixel corresponding to the color component, and the pixel having the larger pixel capacitance is larger. It is characterized in that the area of the overlapping portion is larger than that of a pixel having a smaller pixel capacity. The invention according to claim 8 is the invention according to claim 7, wherein the pixel electrode is formed on the upper layer side of the scanning line and overlaps with a part of the scanning line in the in-plane direction. Each of the pixels is formed, and the area of the polymerized portion is different according to the color component. The invention according to claim 9 is characterized in that, in the invention according to claim 8, the area of the polymerized portion is larger in the pixel having a large pixel capacity than in the pixel having a small pixel capacity. Is what<u style="single">To.</u></p>

<p><u style="single">According to the present invention</u>The level shift voltage ΔV of each of the R, G, and B pixels can be made substantially the same, and thus flicker can be reduced.</p>

FIG. 1 shows a transmission plan view of a part of an active substrate in a color liquid crystal display device according to a first embodiment of the present invention, FIG. 2 shows a cross-sectional view taken along line XX of FIG. 1, and FIG. 3 shows FIG. The cross-sectional view including the facing substrate in the part along the YY line is shown.

As shown in FIG. 3, in this color liquid crystal display device, the active substrate 41 and the opposing substrate 42 located above the active substrate 41 are bonded to each other via a substantially square frame-shaped sealing material (not shown). The liquid crystal 43 is enclosed in the space formed between the sealing material and both substrates 41 and 42.

Then, as shown in FIG. 1, a plurality of scanning lines 44 and a plurality of signal lines 45 are provided on the active substrate 41 extending in the row direction and the column direction, respectively. A thin film transistor 46 connected to both lines 44 and 45 and a pixel electrode 47 driven by the thin film transistor 46 are arranged in a matrix near the intersection of both lines 44 and 45. Further, an auxiliary capacitance line 48 is provided on the side opposite to the scanning line 44 by sandwiching the pixel electrode 47 so as to overlap with the pixel electrode 47 and extend in the row direction.

Next, a specific structure of the thin film transistor 46 and the like will be described with reference to FIG. A scanning line 44 including a gate electrode 51 is provided at a predetermined position on the upper surface of the active substrate 41 (the surface facing the facing substrate 42), and an auxiliary capacitance line 48 is provided at another predetermined location, and the entire upper surface thereof is provided. Is provided with a gate insulating film 52.

A semiconductor thin film 53 made of intrinsic amorphous silicon is provided at a predetermined position on the upper surface of the gate insulating film 52. A channel protection film 54 is provided at substantially the center of the upper surface of the semiconductor thin film 53. Contact layers 55 and 56 made of n-type amorphous silicon are provided on both sides of the upper surface of the channel protection film 54 and on the upper surfaces of the semiconductor thin film 53 on both sides thereof.

A source electrode 57 is provided on the upper surface of one of the contact layers 55. A signal line 45 including a drain electrode 58 is provided at predetermined positions on the upper surface of the other contact layer 56 and the upper surface of the gate insulating film 52.

The thin film transistor 46 is composed of a gate electrode 51, a gate insulating film 52, a semiconductor thin film 53, a channel protective film 54, contact layers 55 and 56, a source electrode 57, and a drain electrode 58.

A flattening film 59 is provided on the entire upper surface of the gate insulating film 52 including the thin film transistor 46 and the like. A contact hole 60 is provided at a portion of the flattening film 59 corresponding to a predetermined portion of the source electrode 57. A pixel electrode 47 made of ITO is provided at a predetermined position on the upper surface of the flattening film 59. The pixel electrode 47 is connected to the source electrode 57 via a contact hole 60.

Next, the opposed substrate 42 will be described with reference to FIG. Black matrix 61 and color filter elements 62R, 62G, 62B of R, G, and B are provided at predetermined positions on the lower surface of the facing substrate 42 (the surface facing the active substrate 41). Of these, the color filter elements 62R, 62G, and 62B are provided so as to face the corresponding pixel electrodes 47.

A common electrode 63 made of ITO is provided on the lower surfaces of the black matrix 61 and the color filter elements 62R, 62G, and 62B. A pixel capacitance portion is formed by the pixel electrode 47, the common electrode 63 arranged opposite to the pixel electrode 47, and the liquid crystal 43 in between. In this case, since the area of the pixel electrode 47 is the same, the pixel capacitance of the pixel capacitance portion is the same.

Here, as shown in FIG. 1, the portion of the auxiliary capacitance line 48 that is overlapped with the pixel electrode 47 is the auxiliary capacitance electrode 48a. Then, the auxiliary capacitance portion is formed by the overlapped portion. In this case, the areas of the auxiliary capacitance electrodes 48a superimposed on the pixel electrodes 47 corresponding to the color filter elements 62R, 62G, and 62B shown in FIG. 3 are reduced in each line width in this order. It's getting smaller. Therefore, the auxiliary capacity of the auxiliary capacity portion decreases in the order of R, G, and B.

By the way, the thicknesses of the color filter elements 62R, 62G, and 62B are different from each other for the purpose of correcting the transmitted light intensity of the liquid crystal 43 for each wavelength of R, G, and B. That is, the thicknesses of the color filter elements 62R, 62G, and 62B are increased in this order.

On the other hand, since the pixel electrodes 47 corresponding to the color filter elements 62R, 62G, and 62B are provided on the flattening film 59, they are arranged on the same plane. Therefore, the gaps d1, d2, and d3 of each pixel of R, G, and B become smaller in this order.

Next, FIG. 4 shows an equivalent circuit of this color liquid crystal display device. Reference numeral 71 indicates a pixel capacitance portion, 72 indicates an auxiliary capacitance portion, and 73 indicates a parasitic capacitance portion between the gate electrode 51 and the source electrode 57 of the thin film transistor 46. In this case, the common electrode 63, which is the electrode on the side of the pixel capacitance section 31 that is not connected to the thin film transistor 46, and the auxiliary capacitance electrode 48a, which is the electrode on the side that is not connected to the thin film transistor 46 of the auxiliary capacitance section 32, are a common power supply (voltage Vcom). It is connected to 74.

Next, FIG. 5 (a) shows the waveform of the voltage applied to the liquid crystal 43, and FIG. 5 (b) shows the scanning voltage (gate pulse) applied to the scanning line 44. Then, when the pixel capacitance of the pixel capacitance section 71 is Clc, the auxiliary capacitance of the auxiliary capacitance section 72 is Cs, and the parasitic capacitance of the parasitic capacitance section 73 is Cgs, the gate pulse is turned off and the image signal of each pixel is captured. At the end, the level shift voltage ΔV obtained by the following equation is generated in the pixel electrode potential Vsig. ΔV = (Cgs) / (Cgs + Clc + Cs)

This level shift voltage ΔV always lowers the pixel electrode potential Vsig by ΔV regardless of the polarity of the signal voltage applied to the signal line 45. Therefore, if the potential Vcom of the common electrode 63 is set lower than the central potential Vc of the signal line 45 by this level shift voltage ΔV, the voltage applied to the liquid crystal 43 becomes a waveform that is almost symmetrical in positive and negative directions, and basically. , Flicker can be prevented.

By the way, as described above, since the thicknesses of the color filter elements 62R, 62G, and 62B are thickened in this order, the gaps d1, d2, and d3 of the pixels of R, G, and B are reduced in this order. There is. The pixel capacitance Clc is represented by ε · S / d (ε: liquid crystal permittivity, S: pixel electrode area, d: gap). Therefore, the pixel capacitance Clc increases as the gap d becomes smaller.

On the other hand, as described above, the areas of the auxiliary capacitance electrodes 48a superimposed on the pixel electrodes 47 corresponding to the color filter elements 62R, 62G, and 62B are smaller in this order. Therefore, the auxiliary capacitance Cs becomes smaller as the area of the auxiliary capacitance electrode 48a becomes smaller.

Then, if the pixel capacitances of the R, G, and B pixels are Clc1, Clc2, and Clc3, then Clc1 &lt;Clc2 &lt;Clc3. If the auxiliary capacities of each pixel of R, G, and B are Cs1, Cs2, and Cs3, then Cs1&gt; Cs2&gt; Cs3. Therefore, if the auxiliary capacitance Cs is corrected so that Clc1 + Cs1 = Clc2 + Cs2 = Clc3 + Cs3, the level shift voltage ΔV of each pixel of R, G, and B can be made the same. Therefore, flicker can be reduced.

Next, as a second embodiment of the present invention, a case of correcting the pixel capacitance Clc will be described with reference to FIG. In FIG. 6, the areas S1, S2, and S3 of the pixel electrodes 47 for R, G, and B decrease in this order. That is, the lower right corner of the pixel electrode 47 for R is not cut out, but the lower right corner of the pixel electrode 47 for G is cut out small, and the lower right corner of the pixel electrode 47 for B is cut slightly larger than that. Missing. In this case, the area of the auxiliary capacitance electrode 48a is the same.

Since the pixel capacitance Clc is represented by ε · S / d, it becomes larger as the gap d becomes smaller, but becomes smaller as the pixel electrode area S becomes smaller. Therefore, if the pixel capacitance Clc is corrected so that S1 / d1 = S2 / d2 = S3 / d3, the level shift voltage ΔV of each pixel of R, G, and B can be made the same. Therefore, flicker can be reduced.

Next, as a third embodiment of the present invention, a case of correcting the parasitic capacitance Cgs will be described with reference to FIG. 7. In FIG. 7, each overlapping area of the pixel electrodes 47 for R, G, and B and the scanning line 44 increases in this order. In this case, the area of the auxiliary capacitance electrode 48a is the same.

The parasitic capacitance Cgs in this case is the total value of the parasitic capacitance between the gate electrode 51 and the source electrode 57 of the thin film transistor 46 and the parasitic capacitance between the overlapping portion between the pixel electrode 47 and the scanning line 44. Of these, the parasitic capacitance between the gate electrode 51 and the source electrode 57 of the thin film transistor 46 is the same for the pixels of R, G, and B. On the other hand, the parasitic capacitance between the overlapping portion between the pixel electrode 47 and the scanning line 44 increases in the order of R, G, and B because the overlapping area increases in the order of R, G, and B.

Therefore, since the level shift voltage ΔV = Cgs / (Cgs + Clc + Cs), even if the pixel capacitance Clc differs due to the difference in the gaps d1, d2, and d3, if this is corrected by the difference in the total parasitic capacitance Cgs, R , G, and B pixels can have the same level shift voltage ΔV. Therefore, flicker can be reduced.

Next, as a fourth embodiment of the present invention, a case where the parasitic capacitance Cgs is corrected by another method will be described. Although not shown, the channel width of each thin film transistor connected to each pixel electrode for R, G, and B is increased in this order. That is, the length in the channel width direction of the source electrode of each thin film transistor connected to each pixel electrode for R, G, and B is increased in this order.

Then, the parasitic capacitance Cgs of each pixel of R, G, and B in this case increases in this order. Therefore, since the level shift voltage ΔV = Cgs / (Cgs + Clc + Cs), even if the pixel capacitance Clc differs due to the difference in the gaps d1, d2, and d3, if this is corrected by the difference in the parasitic capacitance Cgs, R, The level shift voltage ΔV of each pixel of G and B can be the same. That is, when the pixel capacitance of each pixel of R, G, and B is Clc1, Clc2, and Clc3, and the parasitic capacitance Cgs of each pixel of R, G, and B is Cgs1, Cgs2, and Cgs3, then Cgs1 / (Cgs1 + Clc1 +) Cs) = Cgs2 / (Cgs2 + Clc2 + Cs) = Cgs3 / (Cgs3 + Clc3 + Cs). Thereby, flicker can be reduced.

In each of the above embodiments, the transmittance of the color filter elements is increased in the order of R, G, and B, and the thickness of each of the color filter elements R, G, and B is increased in this order. However, the present invention is also applicable when the thicknesses of the color filter elements R, G, and B are thickened in a different order from the above. Further, as described above, the above-described embodiments 1 to 4 may be applied individually, or the above-described embodiments 1 to 4 may be appropriately combined and applied. The combination in this case may be a combination of any two embodiments, a combination of any three embodiments, or a combination of all embodiments. Good.

<figref num="1">FIG. 3 is a transmission plan view of a part of an active substrate in a color liquid crystal display device according to a first embodiment of the present invention.</figref><figref num="2">Sectional view taken along line XX in FIG.</figref><figref num="3">FIG. 5 is a cross-sectional view including a facing substrate in a portion along the YY line in FIG.</figref><figref num="4">The figure which shows the equivalent circuit of the color liquid crystal display device of the said 1st Embodiment.</figref><figref num="5">The figure which shows the waveform of the voltage applied to the liquid crystal of the color liquid crystal display device of the 1st Embodiment.</figref><figref num="6">FIG. 3 is a transmission plan view of a part of an active substrate in a color liquid crystal display device as a second embodiment of the present invention.</figref><figref num="7">FIG. 3 is a transmission plan view of a part of an active substrate in a color liquid crystal display device according to a third embodiment of the present invention.</figref><figref num="8">A transmission plan view of a part of an active substrate in an example of a conventional color liquid crystal display device.</figref><figref num="9">Sectional view taken along line XX in FIG.</figref><figref num="10">FIG. 8 is a cross-sectional view including a facing substrate in a portion along the YY line in FIG.</figref><figref num="11">The figure which shows the equivalent circuit of the said conventional color liquid crystal display device.</figref><figref num="12">The figure which shows the waveform of the voltage applied to the liquid crystal of the said conventional color liquid crystal display device.</figref>

Code description

41 Active board 42 Opposed board 43 LCD 44 scan line 45 signal line 46 thin film transistor 47 pixel electrode 48 Auxiliary capacity line 48a Auxiliary capacitance electrode 62R, 62G, 62B color filter elements 63 Common electrode